Dunseath, OliviaSmith, Edmund J. W.Al-Jeda, T.Smith, James A.King, SophieMay, Paul W.Nobbs, Angela H.Hazell, GavinWelch, Colin C.Su, Bo2019-06-252019-06-252019-06-19Dunseath, O., Smith, E. J. W., Al-Jeda, T., Smith, J. A., King, S., May, P. W., . . . Su, B. (2019). Studies of black diamond as an antibacterial surface for gram negative bacteria: The interplay between chemical and mechanical bactericidal activity. Scientific Reports, 9(1), 1-10.10.1038/s41598-019-45280-2http://hdl.handle.net/10034/622370‘Black silicon’ (bSi) samples with surfaces covered in nanoneedles of length ~5 μm were fabricated using a plasma etching process and then coated with a conformal uniform layer of diamond using hot filament chemical vapour deposition to produce ‘black diamond’ (bD) nanostructures. The diamond needles were then chemically terminated with H, O, NH2 or F using plasma treatment, and the hydrophilicity of the resulting surfaces were assessed using water droplet contact-angle measurements, and scaled in the order O > H ≈NH2 >F, with the F-terminated surface being superhydrophobic. The effectiveness of these differently terminated bD needles in killing the Gram-negative bacterium E. coli was semiquantified by Live/Dead staining and fluorescence microscopy, and visualised by environmental scanning electron microscopy. The total number of adhered bacteria was consistent for all the nanostructured bD surfaces at around 50% of the value for the flat diamond control. This, combined with a chemical bactericidal effect of 20–30%, shows that the nanostructured bD surfaces supported significantly fewer viable E. coli than flat surfaces. Moreover, the bD surfaces were particularly effective at preventing the establishment of bacterial aggregates – a precursor to biofilm formation. The percentage of dead bacteria also decreased as a function of hydrophilicity. These results are consistent with a predominantly mechanical mechanism for bacteria death based on the stretching and disruption of the cell membrane, combined with an additional effect from the chemical nature of the surface.enhttp://creativecommons.org/licenses/by/4.0/Article2045-2322Scientific Reports